Controlled Reversible Visceral Arterial Ischemia, Venous Congestion and Combined Malperfusion via Midline Laparotomy in Rats

The scope of our research is the spectral characterization of physiological and malperfused organs and tissues. Using hyperspectral imaging, we hope to be able to reliably identify and differentiate malperfusion states in different tissues and establish this technology as a new diagnostic pillar in medicine to close existing diagnostic gaps. Current experimental challenges for the spectral characterization of malperfused organs were firstly the lack of experimental protocols for the standardized induction of different malperfusion states, as well as the aim for reversibility.

Our results have paved the way for scientific research questions regarding the systematic investigation of the effect of visceral malperfusion on a biomolecular, spectral, and medical, as well as surgical level with the opportunity for a high temporal resolution as well as reversibility of the malperfusion state. To begin, position the anesthetized rat on the operating table for laparotomy. Perform a seven-centimeter cutaneous incision over the abdomen and dissect the fascia.

Stitch the surgical preparation hooks with attached plastic tubes and surgical mosquito clamps through the skin. Expose the surgical situs using the surgical preparation hooks, applying tension to the tissue. Place a part of a surgical compress below the sternum and resect the xiphoid with strong material scissors.

Using the surgical compress, apply pressure to the resection area to achieve sufficient hemostasis of this well-perfused region. Then mobilize the liver dorsal coddly and dissect the exposed falciform ligament. Using atraumatic preparation instruments, perform a left medialization of the upper abdominal organs to gain access to the left adrenal artery.

Next, identify the pulsating site, medial to the cranial extension of the left adrenal artery. Using overholt clamps, advance through the soft tissue for blunt dissection and tunnel the abdominal aorta at the most cranial end. Sling the aorta with a silicone vessel loop.

Then apply a suitable aneurysm microvascular clamp using the silicone loop to slightly luxate the aorta ventrally, and guide the aneurysm microvascular clamp along the loop to guarantee isolated aortic clamping. Remove the microvascular clamp after the desired time of malperfusion in order to achieve reperfusion of the organs. Employing atraumatic preparation instruments, mobilize the liver to the right and sharply dissect the hepatic ligaments to further lateralize the liver.

Using blunt overholt clamps, open the retrohepatic space at the left crust of the diaphragm and tunnel the caval vein. After slinging the caval vein with a silicone vessel loop, apply a suitable aneurysm microvascular clamp using the loop to slightly ate the vein ventrally. Then advance the aneurysm microvascular clamp along the loop to ensure isolated vein clamping.

Remove the microvascular clamp after the desired time of malperfusion in order to achieve reperfusion of the organs. After slinging the aorta and the caval vein, apply the aneurysm microvascular clamp for both vessels, again, using the silicone loop. Remove the microvascular clamp after the desired time of malperfusion in order to achieve reperfusion of the organs.

Hyperspectral imaging was utilized to validate four distinct malperfusion states. The index parameters for oxygenation and perfusion across five visceral organs were measured, showing a significant reduction in these values during malperfusion compared to normal physiological states. Specifically for the stomach, the established oxygen saturation values range from physiological perfusion at approximately 64.1%to lower values in various malperfusion states, with the lowest being 39.3%for combined arterial and venous malperfusion, indicating severe ischemic conditions.